Can offshore wind farms subdue hurricanes?

The science journal Nature Climate Change published a paper Feb. 26, 2014 suggesting that large arrays of offshore wind turbines could be used to reduce the effects of hurricanes striking the United States.

Is the concept feasible?

According to the paper, offshore windmills strung together could reduce near-surface hurricane wind speeds by 56-92 mph and cut storm surges by 6-79 percent.

The authors, Jacobson et al., base their results primarily on “a global-through-local-climate-weather-air-pollution ocean forecast model” called GATOR-GCMOM. They used it to simulate the effect windmills would have had on Hurricane Katrina, Hurricane Isaac and Superstorm Sandy.

Through cost-benefit analysis they conclude that offshore windmills are more economical than building seawalls and can produce electricity as cheaply as fossil fuels.

Unfortunately, the idea is unrealistic for many reasons:

Ignores up-front cost

Misunderstands the project scope and electric cost

Improbable windmill survivability rate

Enormous up-front cost

Remarkably, the authors totally ignore the cost of building the protective windmill barrier in their cost-benefit analysis. It’s a big oversight: $34.4 trillion!!!

They calculate it would take 964,070 Enercon E126 7.5MW wind turbines to protect the gulf coast and the eastern seaboard.

No offshore wind farm has ever been built in the United States. The E126 wind turbine has never been used in any offshore facility anywhere in the world.

Thus, the construction cost must be estimated based on existing European offshore facilities. The London Array is the largest offshore wind farm in the world. It has 630MW of rated capacity. It cost $3 billion U.S. dollars and went into service in July 2013.

The London Array cost one and a half times as much as an equivalent onshore U.S. farm. A quick review of existing European offshore wind farms shows their construction costs range from one and a half to two times the cost of onshore farms.

It takes 84 Enercon E126 wind turbines to build one 630MW offshore wind farm. According to the numbers, it would take 11,477 ‘London Array’ wind farms to protect the United States.

At $3 billion a pop, the total cost would be $34.4 trillion. That is more than twice the U.S. GDP!

According to author numbers, just to partially protect New Orleans alone from another Hurricane Katrina would cost $2.8 trillion. To protect New York City (but not New Jersey) from another Superstorm Sandy would cost $3.9 trillion!

Misunderstood scope and pricing

In addition to impossibly high up-front construction costs, there are other dumbfounding discrepancies in the cost-benefit analysis.

In Table 1 the authors nonchalantly mention that the gulf coast array would beneficially produce 1.53 terawatts of continuous electricity under normal operations. The east coast array would produce 0.89 terawatts.

The authors apparently don’t realize that it calculates out to an astounding 21,225 terawatt-hours of total electricity. According to 2012 EIA statistics, that is 5.5 times more than all the electricity used in the entire United States!

Who is going to buy all the extra electricity?

In Table 2 the authors claim the levelized cost of “new generation” combined offshore wind turbine electricity is 10.5 cents per kilowatt-hour. Cheap electricity is the added bonus for protecting the country. Their reference is the EIA Annual Energy Outlook for 2013.

If true that would mean combined offshore wind is about the cheapest electricity there is.

However, the EIA reference clearly shows that the levelized cost of new generation offshore wind is the second highest priced electricity there is: $221.5 per megawatt-hour. The highest priced electricity is solar thermal.

Instead of 10.5 cents, the EIA forecasts offshore wind will cost 22.1 cents per kilowatt-hour. That is a huge difference. By comparison, EIA forecasts new generation combined cycle natural gas will cost just 6.5 cents.

Improbable windmill survival rate

Nearly half the turbines in a (wind) farm are likely to be destroyed in a 20-year period– Stephen Rose et al., PNAS, 1/10/2012

Another unlikely assumption made by the authors is that the windmills in their study would survive hurricanes largely unscathed. There is no cost accounting for hurricane damage.

They suggest that large numbers of offshore windmills would reduce hurricane wind speeds enough to insure their survivability in the event of another Katrina.

According to NOAA, Katrina’s offshore wind speeds just before landfall were 131-156 mph. Assuming the author’s mid-point wind reduction of 74 mph is correct, that means each windmill would experience 57-82 mph wind speeds for about 5 hours.

E126 turbines are designed to withstand a maximum wind speed of 76 mpg. They can withstand higher winds for about 10 minutes.

Windmills have cutoff wind speeds for a very good reason. If they didn’t then excessively high electricity generated in high winds would burn out the turbines. Wind turbines, like the E126, are built to slow down and stop in high winds to prevent that from happening.

A 2012 study published by the National Academy of Sciences concluded that, if built, half of all offshore windmills in the Gulf of Mexico would be destroyed within a 20 year period.

The U.S. Department of Energy is considering using offshore wind to boost U.S. electric production from renewable sources up to 20 percent.

The PNAS study suggests design changes to protect turbines from hurricane force winds. Sturdier towers is one. The most meaningful suggestion, though, is the ability to turn turbine blades out of the wind for protection. The E126 can do that.

Conclusions

When something sounds too good to be true, it usually is. A new Nature Climate Change study promises hurricane protection using nearly a million offshore electricity generating wind turbines where none now exist.

If built, it would be an environmentalist’s dream. Not only would it reduce the effects of more intense hurricanes but, unbeknownst to its authors, fill the entire planet’s electric demand with a totally emissions-free, renewable energy source.

It could cut 40-50 percent of the earth’s human-caused CO2 emissions in one fell swoop!

Of course, the $34.4 trillion price tag to build it has to be financed. Electric rate payers will have to accept higher levelized electric rates.

Lastly, windmills have to be specially modified to automatically shut down before being either toppled and/or burnt out during high winds.

In either case, it means that when they are needed most, offshore windmills will provide little land protection in the middle of a hurricane.

Heaven help governments that choose the author suggestion to build windmills instead of seawalls!

Turbines always are equipped with a cut-out around 25 to 30 m/s. When the wind exceeds that they will be switched of. When a wind farm is designed one of the IEC conditions is also looking at the severity of the wind. You will not see any Turbines for this reason in Tornado alley (they have enough oil there.. LOL). I would suggest to also have look at http://www.windbarb.com. It gives you the answers on how much wind energy is possible for any type of turbine and any location in the World.